Process for preparing waterless lithographic masters

ABSTRACT

A novel method of preparing a waterless lithographic master and a method of printing therefrom are provided. To prepare the printing master, a suitable substrate which can be photoconductive or non-photoconductive is imaged with a hydrophobic particulate image pattern and the image fused to the substrate. The imaged substrate is then coated with an aqueous silicone which does not wet the hydrophobic image pattern. The silicone is then heated to selectively provide ink-receptive image areas and ink-releasing non-image areas.

United States Patent 1191 Crystal Sept. 23, 1975 [54] PROCESS FORPREPARING WATERLESS 3,632,375 1/1972 Gipe 96/33 X LITHOGRAPHIC' MASTERS3,640,712 2/1972 Field et a1... 96/33 UX 3,677,178 7/1972 Gipe 96/33 XInventor: Richard y as, Tex. 3,728,123 4/1973 Gipe 96/33 x i 3,772,01611/1973 Anderson et al. 96/33 X [73] Assgnee' Cmpmamnastamfmd, 3,775,11511/1973 Sorkin et al. 96/33 Conn.

[22] Filed: Nov. 14, 1973 Primary Examiner-Norman G. Torchin AssistantExaminerJohn R. Miller [.21] Appl' 415842 Attorney, Agent, or Firm-James.1. Ralabate; James P. OSullivan; Donald M. MacKay [52] US. Cl 96/l.8;96/1 R; 96/33;

101/465 [57] ABSTRACT 1 [51] Int. Cl. G03G 13/00 A novel method ofpreparing a waterless lithographic [58] Field of Search 96/1 R, 1.8, 33;lOl/465 master and a method of printing therefrom are vided. To preparethe printing master, a suitable sub- [561 References C'ted strate whichcan be photoconductive or non- UNITED STATES PATENTS photoconductive isimaged with a hydrophobic partic- 3,088,402 5/1963 Newman 96/1 R "lateimage Pattern and the image fused to the 3,230,081 1/1966 Tomanek etal..... 96/1 R strate. The imaged substrate is then coated with an3,245,784 4/1966 Stricklin 96/ 1.8 aqueous silicone which does not wetthe hydrophobic 3,455,240 7/1969 Martel et al- R X image pattern. Thesilicone is then heated to selecg tively provide ink-receptive imageareas and inkoggett 3,607,255 9/1971 Back 96/1 R releasmg mage areas3,624,227 11/1971 Hwang 96/33 12 Claims, No Drawings PROCESS FORPREPARING WATERLESS LITHOGRAPHIC MASTERS BACKGROUND OF THE iNvENT oN Q,

It has recently been discovered that the need for a fountain solution ona printing press can be obviated if the master is coated in the nonimageareas'with a silicone elastomer which is ink releasing. A number ofdifficulties have been encountered in electrophotographic imaging ofsilicone elastomers. For example, by reason of their abhesive ornonadhesive character, it has been difficult to adhere toner particlesto the silicone in order to provide an image pattern.

BRIEF DEscRiPTioNoF THE INVENTION It has now been discovered that theaforesaid defect can be obviated and printing masters having long imagelives prepared. In addition. it has been found that the master can beimaged, so that the silicone elastomer does not adhere to the image, toprovide inkreceptive image areas and ink releasing nonimage areas whichare durable and long lasting.

More particularly the novel process comprises depositing a hydrophobicparticulate image pattern on a suitable substrate, fusing said patternto said substrate, coating said substrate with an aqueous siliconeemulsion whereby the silicone does not wet the hydrophobic image patternand heating said silicone to provide inkreceptive image areas andink-repellent nonimage areas.

DETAILED DESCRIPTION OF THE lNVENTlOISl Substrates which can be employedto prepare the printing master are self-supporting materials to whichthe silicone and particulate image pattern can be adhered and whichpossess sufficient heat and mechanical stability to permit use underwidely varying printing and handling conditions. and which arepreferably ink accepting. Exemplary of suitable materials are paper;metals such as aluminum; and plastics such as polyester, polycarbonate,polysulfone, nylon and polyurethane, The substrate can bephotoconductive or nonphotoconductive.

Photoconductive" as used herein means electrically photosensitive andconductive in response to activating electromagnetic radiation.

Typical photoconductive organic materials include substituted andunsubstituted organic pigments such as phthalocyanines, for example.copper phthalocyanine, beta form of metal-free phthalocyanine;tetrachlorophthalocyanine; and x-form of metal'free phthalocyanine;quinacridones, as, for example, 2,9-dimethyl quinacridone; 4,1 ldimethylquinacridone; 3,10- dichloro-ol 3-dihydro-quinacridone; 2,9-dimethoxy-6,13-dihydro-quinacridone and 2,4,9,l l-tetrachloroquinacridone;anthraqu inones such as l,5-bis-(betaphenylethylamino) anthraquinone:l,5-bis-( 3 methoxypropylaminoJ an thraquinone; 1.2.5 ,6-di-(Cf'-diphenyl)-thiazole-anthraquinone; HT-hydroxyphcnylmcthoxyamino)anthraquinone; triazines such as 2.4-diaminotriazine; 2,4-di( l-anthraquinonylamino-(H l "-pyrenyl)triazine; 2,4,6 tri-( l '-l ",1pyrenyl )-triazine; azo compounds such as 2,4,6-tris (N'cthyl-paminophenylazo) phloroglucinol; l,3,5.7-tctrahydroxy-2,4,o,8-tetra (N-methyl-N-hydroxy-ethylp-amino-phenylazo)naphthalene; 1,3,5-trihydroxy- 2,4.6-tri (3'-nitro-N-methyl-N-hydroxy-methyl-4 (ill aminophenylazo) benzene; metalsalts and lakes of azo dyes such as calcium lake of 6-bromo-l(l-sulfo-2- naphthylazo)-2-naphthol; barium salt of 6-cyano-l lsulfo-Z-naphthylazo)-2-naphthol; calcium lake of l-(2-azonaphthalene-l"-sulfonic acid)-2-naphthol; calcium lake ofl-(4'-ethyl-5-chloroazo-benzene-2- sulfonic acid)-2-hydroxy-3-naphthoicacid; and mixtures thereof.

Typical inorganic photoconductive compositions include cadmium sulfide,cadmium selenide, cadmium sulfo-selenide, zinc oxide, zinc sulfide,sulfur, selenium,

antimony sulfide, lead oxide, lead sulfide, arsenic sul- I fide,arsenic-selenium, and mixtures thereof.

- The photoconductive materials can be admixed with solid or liquidcarriers and coated on a master substrate by the conventional methods asis well known to those skilled in the art. Typical solid carriersinclude sodium chloride, ammonium chloride, granular silicon, glass,silicon dioxide, steel and nickel. Typical liquid carriers includemineral oil, oleic acid,-peanut oil, kerosene, and trichloroethylene.

In addition the substrate can be a photoconductive polymer. Typicalpolymers include poly-N-vinyl carbazole (PVK),poly-l-vinyl pyrene (PVP),poly-9-vinyl anthracene, polyacenaphthalene, poly-9-(4-pentenyl)-carbazole, poly-9-(5-hexyl)-carbazole, polymethylene pyrene, polylpyrenyl )-butadiene and N-substituted polymeric acrylic acid amides ofpyrene. Also included are derivatives of such polymers including alkyl,nitro, amino, halogen, and hydroxy substituted polymers. Typicalexamples are poly-3-amino carbazole, 1,3- dibromo-poly-N-vinyl carbazoleand 3,6-dibromo-poly- N-vinyl carbazole in particular derivatives of thefor mula where X and Y are substituents and N is an integer. Alsoincluded are structural isomers of these polymers, typical examplesinclude poly-N-vinyl carbazole, poly- 2-vinyl carbazole and poly-3-vinylcarbazole. Also included are co-polymers; typical examples are N-vinylcarbazole/methyl acrylate co-polymer and l-vinyl pyrene/butadiene ABA,and AB block polymers. Typical" nonpolymeric materials includecarbazole, N-

ethylcarbazole, N-phenylcarbazole, pyrene, tetraphene, l-acetylpyrene,2.3-benzochrysene, 6,7 benzopyrene, l-bromopyrene, l-ethylpyrene, l-

l,3,6,8-tetraphenylpyrene chrysene, fluorene,

rene, vinyl chloride and the like in combination with a pigment such ascarbon black. Exemplary of suitable I of the silicone to print from theimaged substrate.

The particulate image pattern can be fused in the conventional mannersuch as in a Xerox heat or vapor fuser but preferably a vapor fuser isemployed when using a catalyst which is thermally degradableorvolatile.i

The silicones which can be employed to coat the substrate are the nonwater curable aqueous gum emulsions, which can be thermally cured, andthe aqueous silicone elastomer emulsions which coalesce upon heating, toprovide ink releasing non-image areas.

Exemplary of suitable silicone gums are those having only methylcontaining groups in the polymer chain such as polydimethylsiloxane;gums having both methyl and phenyl containing groups in the polymerchain as well as gums having both methyl and vinyl groups, methyl andfluorine groups, or methyl, phenyl and vinyl groups in the polymerchain.

Typical silicone gums which are of the thermally curable type suitablefor use in the invention are SylGard No. 182, Syl Off No. 22 and-No. 23manufactured by Dow Corning, Midland, Mich.; Y3557 and Y-3602 siliconegum available from Union Carbide Company,

New York, N.Y., as wellasNo. 4413 silicone and No.

4427 heat curable silicone gums available from General Electric Company,Waterford, N.Y. The Y-3557 and Y-3602 gums specifically have aminoalkanecrosslinking sites in the polymer backbone which react with adiisocyanate crosslinking agent over a wide range of temperature andtime to produce a durable, ink releasable elastomeric film. Theaforesaid gums do not contain a catalyst.

The catalyst employed will depend on the type of gum employed as is wellknown to those skilled in the art. Suitable catalysts for the siliconegums of the conventional type which have been heretofore employedinclude the diaroyl peroxides such as dibenzoyl peroxide,di-p-chlorobenzoyl peroxide and bis-2,4.- dichlorobenzoyl peroxide canbe employed. Other catalysts include the dialkyl peroxides such asdi-t-butyl peroxide and 2,5-dimethyl-2,5-di-(t-butylperoxy)- hexane.Diaralkyl peroxides such as dicumyl peroxide, and alkyl aralkylperoxides such as t-butyl cumyl peroxide can be employed, as well asblocked diisocyanates. The time and temperature relationship forcrosslinking of all of these different types of gums is controlled bythe chemistry of the crosslinking agent employed and a large choice ofagents are available for this purpose. The present invention istherefore not intended to be limited with respect to either time orcuring temperature of these materials, or the specific materials used toachieve crosslinking, although heating at temperature between about50C'and 300C will typically cure or convert the silicone gum to an inkreleasable silicone elastomer.

Other silicones which can be employed and which do not require catalystsare elastomers which coalesce upon heating to include organopolysiloxanecopolymers including'diblock and triblock copolymers, multiblockcopolymers'andgraft copolymers, segmented copolymers, polymer blends,and copolymer stabilized polymer blends. i v

lnk releasable copolymers comprise heterophase polymeric compositionsconsisting of an organopolysiloxane material and a nonsilicone polymericmaterial. Polymeric-materials which can be employed as a component ofthe heterophase polymeric composition and suitable for use in thepresent'invention include thermoplastic materials such as poly(a-methylstyrene), polystyrene, polyesters, polyamides, acrylicpolymers, polyurethanes, and vinyl polymers.

While not limiting, preferred ink release properties of the heteroph asepolymeric compositions requires a ratio by weight of between about to 50parts of the silicone phase to'5 to 50 parts of nonsilicone polymer, theresultant heterophase composition produces a flexible layer of goodmechanical stability for printing as well as optimum ink releaseproperties.

Particularly preferred copolymers having a silicone phase, include thediblock and multiblock copolymers of an organopolysiloxane withpolystyrene and poly (o -methylstyrene). Copolymers of this type andmeth ods for their preparation are described in I and EC ProductResearch,alul-Deve10pmemf, Volume 10, Page l0, (March, 1971) andMacromolecules, Volume 3, Page .1, (January-February, 1970),respectively. q j

The silicone gums are applied in a conventionalmanner, i.e., by solventcasting or dip coating of the substrate or similar techniques, afterdissolution in organic solvents. Typical solvents include benzene,hexane, heptane,-.tetrahydrofuran, toluene .xylene, as well as othercommon aromatic and aliphatic solvents. Many silicones are availablecommercially as aqueous gum emulsions. Aqueous emulsions can be; madefrom the silicone elastomers by dissolving the elastomer in a suitablesolvent such as one of the above, andv mixing with water and anemulsifier as exemplified by the procedure of Example I. I

Curing of the silicone should be done by heat so that the water from theemulsion is evaporated.

After the silico ne is heated to an elastomeric ink releasablecondition, the master can bemounted on a lithographic printing presswith the dampening system removed, whereupon during printing theparticles from the particulate image pattern, may gradually be abradedor dissolved away. Thus it is preferred to employ a master with an inkaccepting substrate, so that one can print from the image depressions,if the image particles are removed. Alternatively, when the substrate isink accepting, the particulate image pattern can'be removed beforemounting the master on the press by treating the master with a solventsuch as acetone, benzene, toluene or other hydrocarbon in whichtheparticulate image material is soluble to reveal an ink acceptingsubstrate.

Typical inks can be employed in the printing method of the inventionwhich have been used in waterless lithographic printing from siliconemasters. Typical inks include inks of the rubber or oleophilic typehaving the vehicle component for the ink pigments derived from variousoleophilic materials such as aromatic and aliphatic hydrocarbons,drying-.oil varnishes lacquers, and solvent type resins.

The-master can be employed in the direct or offset printing-modes withthe dampening system removed.

When the master is employed in the direct mode, the

substrate should be made of a resilient material such as a polyurethane.

The following examples will serve to illustrate the invention. All partsand percentages in said examples and elsewhere in the specification andclaims'are by weight unless otherwise specified.

EXAMPLE I Employing a Xerox Model D Processor, a latent electrostatictest image containing line copy is formed and cascade developed withXerox 3600 dry ink toner on a photosensitive zinc oxide coated printingmaster (Bruning 2000). The toner image is vapor cured by .placing themaster in a Xerox vapor fuser for seven secondsemploying'trichlorethylene. The master is then ;dipped in an aqueous emulsion towet the nonimage areas. The emulsion is prepared by dissolving 95 partsof poly (dimethyl siloxane) gum (Dow Corning Silastic black lithographicink and prints are made from this inked master. The ink is found topreferentially wet the toner image and good prints are obtained withoutthe use of a dampening system.

EXAMPLE II A non-photoreceptive waterless lithographic master isprepared as follows. Employing a Xerox Model D Processor, a latentelectrostatic test image containing line copy is formed and cascadedeveloped with Xerox 3600 dry ink toner. The developed image istransferred from the photoconductive surface of the processor to a sheetof paper coated with a spray. The sheet with the developed image iscontacted with a nonphotoconductive paper master stock and the developedimage electrostatically transferred to the master stock. The toner imageis vapor fused followed by application and curing of the siliconeemulsion as in Example I. When mounted on a Davidson Printing Press withthe dampening system removed. copies of good contrast are obtainedemploying Pope and Gray No. 2441 black lithographic ink.

Having described the present invention with reference to these specificembodiments, it is to be understood that numerous variations can be madewithout departing from the spirit of the invention and it isintended toinclude such reasonable variations and equivalents within the scope.

What is claimed is:

l. A process of preparing a waterless lithographic master comprisingdepositing a hydrophobic particulate image pattern on a suitablesubstrate, fusing said pattern to said substrate, coating saidsubstrate. with a thermally curable but non-water curable aqueoussilicone gum emulsion or an aqueous silicone elastomer emulsion andheating said silicone to selectively provide ink-receptive image areasand ink-repellent nonimage areas.

2. The process of claim 1 wherein the substrate is photoconductive.

3. The process of claim 1 wherein the substrate is non-photoconductive,the particulate image pattern is formed on a photoconductive surface andtransferred to said substrate.

4. The process of claim- 1 wherein the particulate image is fused bysolvent vapor.

5. The process of claim 1 wherein the particulate image pattern is fusedby heat.

6. The process of claim 1 wherein the silicone is an aqueous gumemulsion.

7. The process of claim I wherein the substrate is ink accepting.

8. The process of claim 7 wherein the particulate image pattern isremoved after curing of the silicone.

9. The process of claim 2 wherein the substrate is a zinc oxide coatedpaper.

10. The process of claim 1 wherein the substrate is selected from paper,aluminum, polyester, polycarbonate, polysulfone, nylon and polyurethane.

ll. The process of claim 1 wherein the substrate is paper.

12. A process of printing comprising depositing a hydrophobicparticulate image pattern on a suitable substrate, fusing said patternto said substrate, coating said substrate with a thermally curable butnon-water curable aqueous silicone gum emulsion or an aqueous siliconeelastomer emulsion and heating said silicone to selectively provideink-repellent non-image areas and ink receptive image areas, applyingink to said inkreceptive image areas and contacting the inked masterwith an image-receiving surface to thereby transfer the inked image.

1. A PROCESS OF PREPARING A WATERLESS LITHOGRAPHIC MASTER COMPRISINGDEPOSITING A HYDROPHOBIC PARTICULATE IMAGE PATTERN ON A SUITABLESUBSTRATE, FUSING SAID PATTERN TO SAID SUBSTRATE, COATING SAIDSUBSTRATE, WITH A THERMALLY CURABLE BUT NON-WATER CURABLE AQUEOUSSILICONE GUM EMULSION OR AN AQUEOUS SILICONE ELASTOMER EMULSION ANDHEATING SAID SILICONE TO SELECTIVELY PROVIDE INK-RECEPTIVE IMAGE AREASAND INK-REPELLENT NON-IMAGE AREAS.
 2. The process of claim 1 wherein thesubstrate is photoconductive.
 3. The process of claim 1 wherein thesubstrate is non-photoconductive, the particulate image pattern isformed on a photoconductive surface and transferred to said substrate.4. The process of claim 1 wherein the particulate image is fused bysolvent vapor.
 5. The process of claim 1 wherein the particulate imagepattern is fused by heat.
 6. The process of claim 1 wherein the siliconeis an aqueous gum emulsion.
 7. The process of claim 1 wherein thesubstrate is ink accepting.
 8. The process of claim 7 wherein theparticulate image pattern is removed after curing of the silicone. 9.The process of claim 2 wherein the substrate is a zinc oxide coatedpaper.
 10. The process of claim 1 wherein the substrate is selected frompaper, aluminum, polyester, polycarbonate, polysulfone, nylon andpolyurethane.
 11. The process of claim 1 wherein the substrate is paper.12. A process of printing comprising depositing a hydrophobicparticulate image pattern on a suitable substrate, fusing said patternto said substrate, coating said substrate with a thermally curable butnon-water curable aqueous silicone gum emulsion or an aqueous siliconeelastomer emulsion and heating said silicone to selectively provideink-repellent non-image areas and ink receptive image areas, applyingink to said ink-receptive image areas and contacting the inked masterwith an image-receiving surface to thereby transfer the inked image.